Thermal state in Ordovician mantle and melting mechanism estimated from ultramafic dikes in the Hayachine-Miyamori Ophiolite

Abstract

Ophiolite pulses, periods of high ophiolite formation, have been explained by a super plume model. However, the model fails to explain the absence of high plume activity and the frequent occurrence of subduction-type for the Ordovician ophiolite pulse. We tackle this issue by estimating a mantle potential temperature for the Hayachine-Miyamori Ophiolite. The result shows that the thermal state of the NE-Japan mantle at ~500Ma is not so different from that of the modern mantle.